Given : $$5sec\theta-3tan\theta=5$$
Squaring both sides, we get :
=> $$(5sec\theta-3tan\theta)^2=(5)^2$$
=> $$25sec^2\theta+9tan^2\theta-2(5sec\theta)(3tan\theta)=25$$
Using, $$sec^2\theta-tan^2\theta=1$$
=> $$25(1+tan^2\theta)+9(sec^2\theta-1)-30(tan\theta)(sec\theta)=25$$
=> $$25+25tan^2\theta+9sec^2\theta-9-2(5tan\theta)(3sec\theta)=25$$
=> $$(5tan\theta)^2+(3sec\theta)^2-2(5tan\theta)(3sec\theta)=9$$
=> $$(5tan\theta-3sec\theta)^2=(3)^2$$
=> $$5tan\theta-3sec\theta=3$$
=> Ans - (C)
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